Screen, rear projector, and image display device

ABSTRACT

A screen includes a screen main body that has a diffusion layer, a frame that is provided along the circumference of the screen main body, and to which the diffusion layer is attached through supporting members to rock, and a driving unit that is mounted on the diffusion layer and moves the diffusion layer in parallel to a surface of the diffusion layer.

This is a Continuation of application Ser. No. 11/734,558 filed Apr. 12,2007, which claims foreign priority from the following Japanese PatentApplication: JP 2006-113449, filed Apr. 17, 2006. The disclosure of theprior applications is hereby incorporated by reference herein in theirentirety.

BACKGROUND

1. Technical Field

The present invention relates to a screen, a rear projector, and animage display device.

2. Related Art

In recent years, a projector has been rapidly spread. In addition to afront projection type projector that is mainly used for a presentation,a rear projection type projector has been increasingly recognized as alarge-screen projector. A projection type display device is advantageousin that it can provide a product having the same screen size at a lowcost, as compared with a direct-view-type display, such as a liquidcrystal television or a PDP. However, the direct-view-type displaydevice has become inexpensive, and a high image quality has beenrequired in the projection type display device.

A projector radiates light emitted from a light source onto a lightmodulating element, such as a liquid crystal light valve, projects theprojection light modulated by the light modulating element onto ascreen, and displays an image on the screen. When the image is displayedon the screen, so-called scintillation occurs in which an entire surfaceof the screen flickers.

In this case, a scintillation occurrence principle will be describedwith reference to FIGS. 12A and 12B.

As shown in FIGS. 12A and 12B, light emitted from a light source 70passes through liquid crystal light valves, and is then projected onto ascreen 74 including a diffusion member 72. The projection light that isprojected onto the screen 74 is diffused by the diffusion member 72included in the screen 74. The diffused light is diffracted by thediffusion member 72 at the time of passing through the screen, and actslike a two-dimensional wave. As shown in FIG. 12B, two spherical wavesby the two-dimensional wave are intensified or weakened according to aphase relationship between the two waves, and appears as an interferencefringe between a surface of the screen and a viewer. If the viewerfocuses on an image surface S where the interference fringe isgenerated, the viewer recognizes the interference fringe asscintillation that causes the screen surface to flicker.

The scintillation gives unpleasantness to a viewer viewing the imageformed on the surface of the screen, as if a veil, a cloth, or a cobwebextends between the screen surface and the viewer. Further, the viewerbecomes view a double image like the screen surface and thescintillation through eyes, and focuses on each of the screen surfaceand the scintillation. As a result, the viewer feels fatigued.

In recent years, instead of a high pressure mercury lamp as a lightsource of a projector, it is required for a new light source to bedeveloped. In particular, the laser light source has been anticipated asa light source for a next-generation projector, in terms of energyefficiency, color reproducibility, a long life span, instantaneouslighting, or the like. However, instead of a high pressure mercury lampas a light source of a projector, when using a laser light sourcecausing high interference, contrast of the interference fringe becomeshigher, it becomes hard to endure unpleasantness or fatigue due toscintillation.

Accordingly, various technologies for reducing the scintillation havebeen suggested.

For example, JP-A-11-38512 discloses a screen which includes anemissions-side light diffusion layer that is formed of a plasticmaterial where a light diffusion material is mixed, a middle layer thatis formed of a transparent plastic material, and an incidence-side lightdiffusion layer that is formed of a plastic material where a lightdiffusion material is mixed. According to this screen, the scintillationthat occurs due to the incident-side light diffusion layer is diffusedagain by the emission-side light diffusion layer, which reduces theoccurrence of the scintillation.

Further, JP-A-2001-100316 and JP-A-2001-100317 disclose screens forimage projection in which at least one layer of light diffusion layersforming the screen for image projection is caused to vibrate therein,and thus relative positional relationships between the light diffusionlayers are varied. As such, an internal vibration is applied to thelight diffusion layers, which reduces the occurrence of thescintillation.

However, according to the methods of reducing scintillation that aredisclosed in JP-A-11-38512, JP-A-2001-100316, and JP-A-2001-100317, thefollowing problems are generated.

According to the method disclosed in JP-A-11-38512, since theemission-side light diffusing layer is fixed, a phase distribution in aspace between a screen and a viewer, which is formed by interferencebetween light rays emitted from respective points on a diffusionsurface, is fixed, and an interference fringe is also viewed as a fixedimage. Accordingly, there is a problem in that it is not possible toreduce the scintillation.

According to the methods disclosed in JP-A-2001-100316 andJP-A-2001-100317, since various vibration means, such as light, anelectric field, a magnetic field, a heat, or a stress, are used, anextra driving energy is needed. Further, when using the vibration means,efficiency of an energy transmitted to a diffusion layer is low, and itbecomes difficult for a viewer to comfortably view a screen due tovibrations, sounds, unnecessary electromagnetic waves, exhaust heat, orthe like. Further, when the diffusion layer vibrates in a z direction(focus direction), since an image height is varied, and a location of anoutline of the image in the x-y direction is also varied, which causes adefocus.

SUMMARY

An advantage of some aspects of the invention is that it provides ascreen, a rear projector, and an image display device that are capableof effectively reducing scintillation.

According to a first aspect of the invention, a screen includes a screenmain body that has a diffusion layer, a frame that is provided along thecircumference of the screen main body, and to which the diffusion layeris attached through supporting members to rock, and a driving unit thatis mounted on the diffusion layer and moves the diffusion layer inparallel to a surface of the diffusion layer.

According to this structure, since the diffusion layer of the screenmain body is attached to the frame to rock, when the driving unit isdriven, the diffusion layer moves in parallel to the surface of thediffusion layer. As a result, a diffusion state of the light that haspassed through the diffusion layer of the screen main body is varied,which varies a pattern of an interference fringe that is generated bydiffusion and diffraction of the diffusion layer of the screen mainbody. Therefore, since the light interference is reduced each other, itis possible to reduce the scintillation.

Further, according to this structure, the diffusion layer of the screenmain body moves in parallel to the surface of the diffusion layer, anddoes not move in a direction crossing the surface of the diffusionlayer. In this case, the direction along the surface of the diffusionlayer is defined as the x-y direction, and the direction that crossesthe x-y direction is defined as the z direction. Accordingly, thedefocus can be suppressed while the scintillation can be reduced.Furthermore, since the diffusion layer does not move in the z direction,the surface of the diffusion layer does not generate the air compressingsurface, which suppresses sounds and vibrations from being generated.

Preferably, the supporting members are elastic members.

According to this structure, the power that is supplied from the drivingunit to the diffusion layer of the screen main body is transmitted tothe elastic member. The power that is transmitted to the elastic memberis repulsed from the diffusion layer by means of an elastic force of theelastic member. As a result, in addition to the power supplied from thedriving unit, the diffusion layer of the screen main body is biased bythe elastic member, and moves in parallel to the surface of thediffusion layer. Accordingly, it is possible to further effectively movethe diffusion layer.

Preferably, the driving unit rotates around a rotation shaft thatextends to be substantially vertical to the surface of the diffusionlayer, and the driving unit is mounted on at least one location of thediffusion layer of the screen main body.

According to this structure, since the driving unit rotates around therotation shaft that is vertical to the surface of the diffusion layer,it is possible to make the diffusion layer of the screen main bodycircularly move in parallel to the surface of the diffusion layer.

Further, according to the driving unit, since it is possible to make thediffusion layer circularly move, the motion of the diffusion layerhaving no discontinuous point is possible, different from the case ofthe reciprocal motion. Accordingly, the scintillation can be furtherreduced.

Preferably, the diffusion layer of the screen main body has arectangular shape, the driving units are mounted on at least twolocations of corners of the diffusion layer of the screen main body, andthe driving units that are mounted on the corners of the diffusion layerare simultaneously driven.

According to this structure, the at least two locations of the diffusionlayers of the screen main body are respectively mounted with the drivingunits, and the driving units are simultaneously driven. Therefore, it ispossible to further smoothly move the diffusion layers.

Preferably, the diffusion layer of the screen main body has arectangular shape, and on at least one of sides of the diffusion layerof the screen main body which face each other, a guide unit is providedto slidably move the diffusion layer in a direction along the side.

According to this structure, since the guide unit is provided along theside of the diffusion layer (in parallel to the surface of the diffusionlayer), it is possible to surely prevent the diffusion layer from movingin the z direction.

Preferably, the screen main body has a plurality of diffusion layers,the plurality of diffusion layers are disposed on an optical path axisof light that is projected onto the plurality of diffusion layers, atleast two diffusion layers of the plurality of diffusion layers areattached to the frame through the supporting members to rock, and thedriving unit is mounted on at least one of the plurality of diffusionlayers that are attached to the frame through the supporting members.

According to this structure, since the plurality of diffusion layers areattached to the frame through the supporting members to rock and thedriving units are mounted on the diffusion layers, each of the pluralityof diffusion layers relatively moves. As a result, the locations of theplurality of diffusion layers are relatively varied, and the diffusionstate of the light that passes through the screen is temporally varied,which varies the pattern of the interference fringe that is generated bydiffusion and diffraction of the diffusion layers of the screen mainbody. Accordingly, as compared with the case where the diffusion layeris a single layer, since the plurality of diffusion layers can berelatively moved, the pattern of the interference fringe is integrallyaveraged by means of a residual image effect of eyes of the viewer, andthe scintillation can be more effectively reduced.

Preferably, at least portions of neighboring diffusion layers among theplurality of diffusion layers attached to the frame through thesupporting members come into contact with each other, and the drivingunit is mounted on at least one diffusion layer of the diffusion layerscoming into contact with each other.

According to this structure, when the driving unit is mounted on onediffusion layer among the plurality of diffusion layers attached to theframe, the power that is transmitted from the driving unit to thediffusion layer is transmitted to the neighboring diffusion layers dueto the friction of the contact portions. Accordingly, it is possible tomanually move the diffusion layers on which the driving units are notmounted, and the scintillation can be more effectively reduced.

Preferably, the supporting member that corresponds to each of thediffusion layers attached to the frame has a different resonancefrequency.

According to this structure, since the supporting member thatcorresponds to each of the diffusion layers has the different resonancefrequency, each of the diffusion layers vibrates at each resonancefrequency. As a result, since each of the diffusion layers can beindividually vibrated, it is possible to further effectively reduce thescintillation.

Preferably, a resonance frequency of the supporting member and a drivingfrequency of the driving unit are substantially equal to each other.

According to this structure, since the resonance frequency of thesupporting member and the driving frequency of the driving unit aresubstantially equal to each other, it is possible to effectively drivethe diffusion layer with low energy.

According to a second aspect of the invention, a rear projector includesa light source that emits light, a light modulating element thatmodulate the light emitted from the light source, and theabove-described screen onto which the light modulated by the lightmodulating element is projected.

According to this structure, since the screen is included, it ispossible to provide a rear projector in which the scintillation isreduced.

According to a third aspect of the invention, an image display deviceincludes a light source that emits light, the above-described screen,and a scanning unit that scans the light emitted from the light sourceon the screen.

According to this structure, since the screen is included, it ispossible to provide an image display device in which the scintillationis reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, where like numbers refer like elements.

FIGS. 1A and 1B are diagrams illustrating a schematic structure of arear projector according to an embodiment of the invention.

FIG. 2 is a diagram illustrating a schematic structure of a projectionoptical system of a rear projector according to an embodiment of theinvention.

FIG. 3 is a diagram illustrating a schematic structure of a screenaccording to a first embodiment of the invention.

FIG. 4 is a diagram illustrating a schematic structure of a screenaccording to a second embodiment of the invention.

FIG. 5 is a diagram illustrating a schematic structure of a screenaccording to a third embodiment of the invention.

FIG. 6 is a diagram illustrating a schematic structure of a screenaccording to a fourth embodiment of the invention.

FIGS. 7A to 7D are plan views illustrating a screen that circularlymoves when a motor is driven.

FIGS. 8A and 8B are diagrams illustrating a schematic structure of ascreen according to a fifth embodiment of the invention.

FIG. 9 is a diagram illustrating a schematic structure of a screenaccording to a sixth embodiment of the invention.

FIG. 10 is a diagram illustrating a schematic structure of a screen mainbody that has a plurality of diffusion function layers.

FIG. 11 is a diagram illustrating a schematic structure of a screenaccording to a seventh embodiment of the invention.

FIGS. 12A and 12B are diagrams illustrating scintillation.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, preferred embodiments of the invention will be describedwith reference to the accompanying drawings.

The scale of each layer or member has been adjusted in order to have arecognizable size in the respective drawings used in the belowdescription. Further, in the description below, a xyz orthogonalcoordinate system is set, and positional relationships among respectivemembers will be described with reference to the xyz orthogonalcoordinate system. In addition, a predetermined direction in ahorizontal plane is defined as an x direction, a direction that isorthogonal to the x direction in the horizontal plane is defined as a ydirection, and a direction that is orthogonal to each of the x and ydirections is defined a z direction. In this embodiment, a front side ofa screen 20 is defined as a viewer side where a viewer views an image,and a reverse side thereof is defined as a rear side.

FIRST EMBODIMENT

FIG. 1A is a perspective view illustrating a schematic structure of arear projector 120 according to an embodiment of the invention. FIG. 1Bis a side cross-sectional view illustrating the rear projector 120 shownin FIG. 1A. In the rear projector 120 according to this embodiment,light emitted from a light source is modulated by a light modulatingunit, and the modulated light is projected onto a screen 20 to bediffused.

As shown in FIG. 1A, the rear projector 120 includes the screen 20 ontowhich an image is projected, and a casing 90 that is mounted on a sideof a rear surface of the screen 20. A front panel 88 is provided at aportion of the casing 90 below the screen 20, and openings 38 foroutputting a sound from a speaker are provided at left and right sidesof the front panel 88.

Next, an inner structure of the casing 90 of the rear projector 120 willbe described.

As shown in FIG. 1B, a projection optical system 150 is disposed on alower side of an inner portion of the casing 90 in the rear projector120. Reflective mirrors 92 and 94 are provided between the projectionoptical system 150 and the screen 20. The light emitted from theprojection optical system 150 is reflected on the reflective mirrors 92and 94, and is projected onto the screen 20 to be diffused.

Next, a schematic structure of the projection optical system 150 of therear projector 120 will be described.

FIG. 2 is a diagram illustrating a schematic structure of a projectionoptical system 150 of a rear projector 120. In FIG. 2, the casing 90that forms the rear projector 120 is omitted for the purpose ofsimplification.

The projection optical system 150 includes a light source 102, a lightmodulating element 100 that modulates the light emitted from the lightsource 102, and projection lenses 114 that projects the light modulatedby the light modulating element 100. In this embodiment, liquid crystallight valves 100R, 100G, and 100B are used as the light modulatingelement 100.

As shown in FIG. 2, the projection optical system 150 is provided withthe light source 102 that is a lamp unit that is composed of a whitelight source, such as a halogen lamp. The light that is emitted from thelight source 102 to be the lamp unit is split into three primary colorsof RGB by means of three mirrors 106 and two dichroic mirrors 108 thatare disposed in the projection optical system 150, and is guided toliquid crystal light valves 100R (red), 100G (green), and 100B (blue)corresponding to the respective primary colors. In this case, the liquidcrystal light valves 100R, 100G, and 100B are respectively driven inaccordance with signals of the primary colors of R, G, and B supplied byan image signal processing circuit (not shown).

Further, a B (blue) light component has a long optical path as comparedwith the other R (red) or G (green) light components. In order toprevent an optical loss, the B light component is guided through a relaylens system 121 that is composed of an incident lens 122, a relay lens123, and an emission lens 124.

The light beams that are respectively modulated by the liquid crystallight valves 100R, 100G, and 100B are incident on a dichroic prism 112in three directions (liquid crystal light valves 100R, 100G, and 100B).The dichroic prism 112 refracts the R light component and the B lightcomponent at 90 degrees, and makes the G light component go straight,such that the light components emitted from light emission portions ofthe respective liquid crystal light valves 100R, 100G, and 100B aresynthesized. In addition, the light that is emitted from each lightemission portion and is synthesized is projected onto the screen 20through the projection lens 114.

Next, a schematic structure of the screen 20 of the rear projector 120will be described.

FIG. 3 is a plan view illustrating a schematic structure of a screen 20.In FIGS. 3 to 9, a screen main body 12 is disposed at a predeterminedgap with a frame 16. However, in actual, as shown in FIGS. 1A and 1B, aportion of the frame 16 protrudes to the front surface of the frame mainbody 12, and the gap is covered with the protruding frame 16.

As shown in FIG. 3, the screen 20 includes the screen main body 12,springs 14, the frame (frame portion) 16, and a crank motor 22 (drivingunit).

The screen main body 12 has a rectangular diffusion plate 10 (diffusionlayer) in plan view. The diffusion plate 10 diffuses the light projectedonto the screen main body 12 and expands a visual field of a viewer. Inthe diffusion plate 10, a diffusion material is uniformly dispersed. Asthe diffusion material, silicon oxide, alumina, calcium carbonate, glassbead, a copolymer such as an acrylic resin system, or an amorphousorganic system material such as a silicon resin system are preferablyused. Further, a hard coat layer (not shown) that protects the screenmain body 12 including the diffusion plate 10 or the like is provided onthe surface of the diffusion plate 10 at the side of the viewer.

The frame 16 is formed in a frame shape along the circumference of thediffusion plate 10, and is constructed to be integrated with the casing90 shown in FIGS. 1A and 1B. The frame 16 and the diffusion plate 10 aredisposed at a predetermined gap therebetween, and upper corners of thediffusion plate 10 are attached to the frame 16 through the springs 14(elastic members) so as to rock (so as to wobble). That is, thediffusion plate 10 of the screen main body 12 suspends from the frame 16by the springs 14. Further, in addition to the springs 14, an elasticmember, such as a rubber member, which can expand and contract, may beused. Furthermore, in addition to the springs 14 and the elastic member,a supporting member, such as a wire, which can suspend the diffusionplate 10, may be used.

On an outer circumferential surface 16 a of a lower left portion of theframe 16, the crank motor 22 is mounted. The crank motor 22 is connectedto a control unit 24 that is provided in the casing 90. Further, thecrank motor 22 is disposed such that its rotation shaft C is vertical toa surface of the diffusion plate 10. At a front end of the rotationshaft C, a rectangular plate member 50 is attached such that a surfaceof the plate member 50 is vertical to the rotation shaft C. A connectingrod 52, which extends to be vertical to the surface of the plate member50, is attached to a corner of the plate member 50 shifted from thecenter (rotation shaft C) of the plate member 50.

Meanwhile, at a lower left corner of the diffusion plate 10 of thescreen main body 12, a connecting rod 26 is mounted which extends to bevertical to the surface of the diffusion plate 10.

In addition, the connecting rod 52 of the crank motor 22 and theconnecting rod 26 of the diffusion plate 10 are connected to each otherby a ring-shaped rubber member 28. As a result, if the crank motor 22 isdriven, the diffusion plate 10 can rotate around the rotation shaft C.

According to this embodiment, since the diffusion plate 10 of the screenmain body 12 is attached to the frame 16 to rock, if the crank motor 22is driven, the diffusion plate 10 moves in parallel to the surface ofthe diffusion plate 10 (x-y direction). As a result, a diffusion stateof the light that passes through the diffusion plate 10 of the screenmain body 12 is changed, and thus a pattern of an interference fringethat is generated by diffusion and diffraction of the diffusion plate 10of the screen main body 12 is changed. Accordingly, since theinterference of light is reduced, it is possible to reducescintillation.

Further, according to this embodiment, the diffusion plate 10 of thescreen main body 12 moves in parallel to the surface of the diffusionplate 10 (x-y direction), and does not move in a z direction orthogonalto the surface of the diffusion plate 10. Accordingly, defocus can besuppressed while scintillation is reduced. Furthermore, since thediffusion plate 10 of the screen main body 12 does not move in a zdirection, the surface of the diffusion plate 10 does not form an aircompressing surface, a sound and a vibration can be suppressed frombeing generated.

Furthermore, according to this embodiment, since the diffusion plate 10is attached to the frame 16 through the springs 14, a power that issupplied from the motor 22 to the diffusion plate 10 of the screen mainbody 12 is transmitted to the springs 14. The power that has beentransmitted to the springs 14 is repulsed from the diffusion plate 10 bymeans of an elastic force of the springs 14. As a result, in addition tothe power supplied from the motor 22, the diffusion plate 10 of thescreen main body 12 is biased by the springs 14, and moves in parallelto the surface of the diffusion plate 10. Accordingly, it is possible tofurther effectively move the diffusion plate 10.

Furthermore, according to this embodiment, since the motor 22 can rotatearound the rotation shaft C that is vertical to the surface of thediffusion plate 10, it is possible to make the diffusion plate 10 of thescreen main body 12 perform an eccentrically circular motion in parallelto the surface of the diffusion plate 10.

Further, according to the crank motor 22, since it is possible to makethe diffusion plate 10 perform an eccentrically circular motion, thediffusion plate 10 where there is not a discontinuous point can move,different from the case of a reciprocating motion. Therefore, it ispossible to further reduce the scintillation.

SECOND EMBODIMENT

Next, a second embodiment of the invention will be described withreference to the accompanying drawings.

In the first embodiment, the diffusion plate suspends from the framethrough the elastic members. However, in the second embodiment, aplurality of places of the diffusion plate are attached to the framethrough the elastic members, different from the first embodiment.Further, since the other structure of the rear projector is the same asthat of the first embodiment, the common constituent elements aredenoted by the same reference numerals and the detailed descriptionthereof is omitted.

FIG. 4 is a plan view illustrating a schematic structure of a screen 20.

Rubber members 14 are disposed at equal intervals along thecircumference of the diffusion plate 10, and the diffusion plate 10 isattached to the frame 16 through the rubber members 14. As a result, thediffusion plate 10 is elastically supported by means of the rubbermembers 14 that are inserted between the diffusion plate 10 and theframe 16, and the diffusion plate 10 can rock in parallel to the surfaceof the diffusion plate 10 (x-y direction).

On the lower right side of the diffusion plate 10 of the screen mainbody 12 at the rear side, the above-described crank motor 22 is mounted.The crank motor 22 is connected to a control unit 24 that is provided inthe casing 90.

Even in this embodiment, it is possible to achieve the same function andeffect as the first embodiment.

Further, the member that is inserted between the diffusion plate 10 andthe frame 16 is not limited to the rubber member, but may be the elasticmember such as the spring, or an oil damper.

THIRD EMBODIMENT

Next, a third embodiment of the invention will be described withreference to the accompanying drawings.

In the second embodiment, one driving unit is mounted in the diffusionplate, but in the third embodiment, a plurality of driving units aremounted in the diffusion plate, different from the second embodiment.Further, since the other structure of the rear projector is the same asthat of the first embodiment, the common constituent elements aredenoted by the same reference numerals and the detailed descriptionthereof is omitted.

FIG. 5 is a plan view illustrating a schematic structure of a screen 20.

Rubber members 14 are disposed at equal intervals along thecircumference of the diffusion plate 10, and the diffusion plate 10 isattached to the frame 16 through the rubber members 14. As a result, thediffusion plate 10 is elastically supported by means of the rubbermembers 14 that are inserted between the diffusion plate 10 and theframe 16, and the diffusion plate 10 can rock in parallel to the surfaceof the diffusion plate 10 (x-y direction).

At four corners of the diffusion plate 10 at the rear side, the crankmotors 22 are mounted. Each of the crank motors 22 is connected to acontrol unit 24 that is provided in the casing 90. The control unit 24synchronizes driving cycles of the four crank motors 22 and suppliesdriving signals to the four crank motors 22, and controls the rotationspeed and the rotation direction of the four crank motors 22 such thatthey become equal to one another. Alternatively, deceleration gears forvarying the driving cycles of the crank motors 22 may be provided, andthe crank motors 22 may be driven in a state where the crank motors 22are different from one another in the rotation speed and the rotationdirection.

According to this embodiment, the four corners of the diffusion plate 10of the screen main body 12 are mounted with the crank motors 22, and thecrank motors 22 are simultaneously driven. Therefore, it is possible tosmoothly move the diffusion plate 10.

FOURTH EMBODIMENT

Next, a fourth embodiment of the invention will be described withreference to the accompanying drawings.

In the third embodiment, the respective driving units are continuouslydriven, but in the fourth embodiment, the respective driving units areintermittently driven, different from the third embodiment. Further,since the other structure of the rear projector is the same as that ofthe first embodiment, the common constituent elements are denoted by thesame reference numerals and the detailed description thereof is omitted.

FIG. 6 is a plan view illustrating a schematic structure of a screen 20.FIGS. 7A to 7D are diagrams illustrating an operation of a screen 20.

As shown in FIG. 6, at four corners of the diffusion plate 10 at therear side, DC motors 22 (driving units) are mounted. Each of the DCmotors 22 is connected to a control unit 24 that is provided in thecasing 90. The control unit 24 synchronizes driving cycles of the fourDC motors 22 and supplies driving signals to the four DC motors 22, andcontrols the rotation speed and the rotation direction of the four DCmotors 22 such that they become equal to one another.

Further, on the rear surface side of the diffusion plate 10, a positiondetecting sensor 32 is provided to detect a position of the diffusionplate 10. The position detecting sensor 32 is provided at a positionwhere stopped is an operation of the diffusion plate 10 rotating bymeans of a biasing force at the time of the DC motor 22 being driven,when the driving of the DC motor 22 is stopped. In this embodiment, theposition is referred to as a driving stopping position. Further, theposition detecting sensor 32 is connected to the control unit 24,converts test light reflected on the diffusion plate 10 into an electricsignal, and supplies the converted electric signal to the control unit24.

Next, the operation of the diffusion plate 10 will be described withreference to FIGS. 6, and 7A to 7D.

As shown in FIGS. 6, 7A, and 7B, if the driving signal is supplied fromthe control unit 24 to the DC motors 22, the four DC motors 22 that arelocated at the four locations are driven. As a result, the diffusionplate 10 that is connected to the DC motors 22 rotates in a clockwisedirection in 7A to 7D.

At this time, since the position detecting sensor 32 and the diffusionplate 10 overlap each other in plan view, the position detecting sensor32 detects the diffusion plate 10. For this reason, the control unit 24continuously supplies the driving signal to the DC motors 22.

Next, as shown in FIG. 7C, if the diffusion plate 10 rotates to thedriving stopping location, since the position detecting sensor 32 andthe diffusion plate 10 do not overlap each other in plan view, theposition detecting sensor 32 does not detect the diffusion plate 10. Forthis reason, the control unit 24 stops the supply of the driving signalto the DC motor 22. Even this case, the diffusion plate 10 rotates bymeans of the biasing force of the DC motor 22.

Subsequently, even when the diffusion plate 10 rotates to the locationshown in FIG. 7D, since the position detecting sensor 32 and thediffusion plate 10 does not overlap each other in plan view, theposition detecting sensor 32 does not detect the diffusion 10. For thisreason, the control unit 24 maintains the state where the supply of thedriving signal to the DC motor 22 is stopped.

In addition, if the diffusion plate 10 rotates again to the locationshown in FIG. 7A, the position detecting sensor 32 detects the diffusionplate 10, and the control unit 24 supplies the driving signal to the DCmotor 22.

As such, in this embodiment, if the diffusion plate 10 rotates to thedriving stopping location, the driving of the DC motor 22 is stopped. Inthe other cases, the DC motor 22 is driven, and the DC motor 22 isintermittently driven.

According to this embodiment, the same function and effect as the firstembodiment can be achieved, and the diffusion plate 10 can move with asmall energy.

FIFTH EMBODIMENT

Next, a fifth embodiment of the invention will be described withreference to the accompanying drawings.

In the first embodiment, the corners of the diffusion plate are attachedto the frame by using the elastic members. However, in the fifthembodiment, guide units are provided in the diffusion plate, differentfrom the first embodiment. Further, since the other structure of therear projector is the same as that of the first embodiment, the commonconstituent elements are denoted by the same reference numerals and thedetailed description thereof is omitted.

FIG. 8A is a plan view illustrating a schematic structure of a screen20. FIG. 8B is a perspective view illustrating a screen 20 shown in FIG.8A.

At a left side 10 a and a right side 10 b of the diffusion plate 10 ofthe screen main body 12 that face each other, elongated rectangularguide mechanisms 30 and 30 (guide units) are provided. In the surfaces30 a and 30 a of the guide mechanisms 30 and 30 that face the diffusionplate 10, guide grooves 34, which extend along a longitudinal directionof the guide mechanisms 30 and 30, are formed. At both ends of the guidegroove 34 in a longitudinal direction, anti-slipping portions 36 and 36are provided to stop the sliding of the diffusion plate 10.

The upper corners of the diffusion plate 10 are attached to the frame 16through the elastic members 14, such as rubber members, to rock.Further, a linear motor 22, which can reciprocate, is attached to thelower periphery of the diffusion plate 10 of the screen main body 12.

According to this embodiment, since the guide mechanisms 30 are providedalong the sides 10 a and 10 b of the diffusion plate 10, the diffusionplate 10 moves in parallel to the surface of the diffusion plate 10 (ydirection). Accordingly, it is possible to surely prevent the diffusionplate 10 from moving in a z direction. Further, defocus can becontrolled while scintillation is reduced.

SIXTH EMBODIMENT

Next, a sixth embodiment of the invention will be described withreference to the accompanying drawings.

In the above-described embodiments, the screen main body is composed ofa single layer diffusion plate. However, in the sixth embodiment, thescreen main body is composed of a plurality of diffusion plates,different from the above-described embodiments. Further, since the otherstructure of the rear projector is the same as that of the firstembodiment, the common constituent elements are denoted by the samereference numerals and the detailed description thereof is omitted.

FIG. 9 is a perspective view illustrating a schematic structure of ascreen main body 12 according to a sixth embodiment of the invention.FIG. 10 is a diagram illustrating structures of a plurality of diffusionplates.

As shown in FIGS. 9 and 10, the screen main body 12 includes diffusionplates 10, a lenticular lens 42 that compresses (condenses) the image,and a Fresnel lens 40 that converts the light projected onto the screen20 into collimated light. These components are disposed in the order ofthe diffusion plates 10, the lenticular lens 42, and the Fresnel lens 40when viewed from the viewer, on the optical axis L of the projectedlight.

A hard coat layer is provided on a surface of the diffusion plate 10 atthe side of the viewer. Further, black masks 44 are formed in a latticeon the surface of the lenticular lens 42 at the side of the viewer.

As shown in FIG. 9, the diffusion plates 10, the lenticular lens 42, andthe Fresnel lens 40 are attached to the frame 16 through the springs 14,14, and 14 to rock. Further, the diffusion plates 10, the lenticularlens 42, and the Fresnel lens 40 are mounted with the crank motors 22,respectively. A connecting rod 52 is attached to each of the crankmotors 22, and a connecting rod 26 corresponding to the connecting rod52 is attached to each of the diffusion plates 10, the lenticular lens42, and the Fresnel lens 40. In addition, the connecting rods 52 of therespective crank motors 22, and the connecting rods 26 of the diffusionplates 10, the lenticular lens 42, and the Fresnel lens 40 are connectedto each other by means of ring-shaped rubber members 28.

In this embodiment, resonance frequencies of the springs 14, 14, and 14that are attached to the diffusion plates 10, the lenticular lens 42,and the Fresnel lens 40 are different from one another. Elastic modulusof each of the springs 14, 14, and 14 may be caused to be different,such that each resonance frequency may be different. Further, the crankmotors 22 are independently mounted on the diffusion plates 10, thelenticular lens 42, and the Fresnel lens 40, and thus a driving periodof each of the crank motors 22 may be different. Alternatively, thecombination thereof may be used.

According to this embodiment, the plurality of diffusion plates 10 areattached to the frame 16 through the springs 14 to rock, and the crankmotors 22 are mounted on the diffusion plates 10. Therefore, each of theplurality of diffusion plates 10 relatively moves. As a result, ascompared with the case where a single layer diffusion layer is used,even when the diffusion plates 10 slightly move, the diffusioncharacteristic and the pattern of the interference fringe are varied.Accordingly, the interference fringe is integrally averaged by means ofa residual image effect of eyes of the viewer, and the scintillation canbe more effectively reduced.

Further, the diffusion plate 10, the lenticular lens 42, and the Fresnellens 40 are preferably disposed such that at least portions of them comeinto surface contact with one another. In this case, at least one layeramong the diffusion plate 10, the lenticular lens 42, and the Fresnellens 40, for example, the crank motor 22 may be only mounted on thediffusion plate 10.

As a result, the power that is transmitted from the motor 22 to thediffusion plate 10, the lenticular lens 42, and the Fresnel lens 40 istransmitted to the neighboring layers due to the friction of the contactportions. Accordingly, it is possible to manually move the diffusionplate 10, the lenticular lens 42, and the Fresnel lens 40 on which thecrank motors 22 are not mounted, and the scintillation can be moreeffectively reduced.

SEVENTH EMBODIMENT

Next, a seventh embodiment of the invention will be described withreference to the accompanying drawings.

In this embodiment, the light modulating element and a scanning unit areused as the structure of the rear projector. In this point, thisembodiment is different from the above-described embodiments. Further,since the other structure of the rear projector is the same as that ofthe first embodiment, the common constituent elements are denoted by thesame reference numerals and the detailed description thereof is omitted.

FIG. 11 is a cross-sectional view illustrating a schematic structure ofa rear projector 120.

As shown in FIG. 11, the rear projector 120 according to this embodimentincludes a light source 102 that emits laser light, a lens opticalsystem 103 that includes a collimated optical system 104 and a beamshaping optical system 105, a scanner 82 that scans the incident laserlight in a two-dimensional direction, a projection lens 108 thatprojects the scanned light to be diffused, and a reflective mirror 109that reflects the projected light toward the screen 120. The lightsource 102 includes a red laser diode 102R that emits red laser light, agreen laser diode 102G that emits green laser light, and a blue laserdiode 102B that emits blue laser light.

The laser light that is emitted from the laser diodes 102R, 102G, and102B is incident on the scanner 82 through the lens optical system 103.The incident laser light is scanned in a two-dimensional direction bythe scanner 82, and is then projected onto the screen 20 through theprojection lens 108 and the reflective mirror 109. In this way, the rearprojector 120 according to this embodiment causes the scanner 82 to scanthe laser light emitted from the light source 102 on the screen 20,thereby forming an image.

As in this embodiment, even in the scan-type rear projector 120 usingthe laser light source, since the screen 20 can move by the driving unit22, the same function and effect as the above-described embodiment canbe achieved, and the scintillation can be effectively reduced.

The technical range of the invention is not limited to theabove-described embodiments, and various modifications and changes canbe made without departing from the sprit and scope of the invention.

For example, in the above-described embodiments, the crank motor or theDC motor is used as the driving unit, but a piezoelectric actuator maybe used. In addition, a displacement of the piezoelectric actuator maybe increased by using an amplifying unit, and may be transmitted to thediffusion plate 10.

Further, the rotation frequency of the crank motor is set to besubstantially equal to an oscillation frequency (resonance frequency) ofthe diffusion plate (and the lenticular lens, the Fresnel lens, or thelike), and oscillation of the set frequency of the motor may be appliedto the diffusion plate. As a result, since the diffusion plateresonates, it is possible to effectively drive the diffusion plate orthe like with the low energy.

In the above-described embodiments, the transmissive liquid crystallight valve is used as the light modulating element. However, areflective liquid crystal light valve and a small-sized mirror arraydevice can be used as the light modulating element. At this time, astructure of the projection optical system is appropriately changed.

The entire disclosure of Japanese Patent Application No.2006-113449,filed Apr. 14, 2006 is expressly incorporated by reference herein.

1. A screen comprising: a screen main body that has a plurality ofdiffusion layers, the plurality of diffusion layers being disposed on anoptical path axis of light that is projected onto the plurality ofdiffusion layers; a frame that is provided along a circumference of thescreen main body, at least two diffusion layers of the plurality ofdiffusion layers being attached to the frame through supporting membersto rock; and a plurality of driving units, each driving unit isindividually mounted on a respective one of the diffusion layersattached to the frame through the supporting members, the plurality ofdriving units being configured to move the diffusion layers in parallelto a surface of the diffusion layers.
 2. The screen according to claim1, wherein the supporting members are elastic members.
 3. The screenaccording to claim 1, wherein each driving unit rotates around arotation shaft that extends to be substantially vertical to the surfaceof the diffusion layers, and each driving unit is mounted on at leastone location of the diffusion layers.
 4. The screen according to claim1, wherein the diffusion layers of the screen main body have arectangular shape, and on at least one of sides of the diffusion layers,a guide unit is provided to slidably move the diffusion layers in adirection along the side.
 5. The screen according to claim 1, wherein atleast portions of neighboring diffusion layers come into contact witheach other.
 6. The screen according to claim 1, wherein the supportingmembers have a different resonance frequency.
 7. The screen according toclaim 1, wherein a resonance frequency of the supporting members and adriving frequency of the driving units are substantially equal to eachother.
 8. A rear projector comprising: a light source that emits light;a light modulating element that modulates the light emitted from thelight source; and the screen according to claim 1 onto which the lightmodulated by the light modulating element is projected.
 9. An imagedisplay device comprising: a light source that emits light; the screenaccording to claim 1; and a scanning unit that scans the light emittedfrom the light source on the screen.